High purity lithium polyhalogenated boron cluster salts useful in lithium batteries

Abstract

The present invention relates to lithium secondary batteries comprising a negative electrode, a positive electrode, a separator and a lithium-based electrolyte carried in an aprotic solvent, and to the electrolyte compositions. The electrolyte comprises a lithium salt of the formula: Li 2 B 12 F x H 12-x-y Z y where x+y is from 3 to 12, and x and y are independently from 0 to 12, and Z comprises at least one of Cl and Br.

1. A lithium ion secondary battery comprising:
 an anode, a cathode, a separator and an electrolyte comprising: at least one organic aprotic carrier and 
 at least one lithium salt of the formula:
   Li 2 B 12 F x H 12-x-y Z y    
 
 
       where x is greater than or equal to 8 and x+y is from 8 to 12, and Z comprises at least one of Cl and Br, and wherein the electrolyte is substantially free of non-lithium alkali metals. 
     
     
       2. The battery of  claim 1  wherein the anode comprises at least one member selected from the group consisting of carbon, tin oxide, silicon compounds and germanium compounds. 
     
     
       3. The battery of  claim 1  wherein the cathode comprises lithium composite oxide. 
     
     
       4. The battery of  claim 1  wherein the carrier comprises at least one member selected from the group consisting of ketones, carbonates, esters, and alcohols. 
     
     
       5. The battery of  claim 1  wherein the electrolyte further comprises at least one other lithium based salt. 
     
     
       6. The battery of  claim 1  wherein the separator comprises at least one member selected from the group consisting of nylon, cellulose, nitrocellulose, polysulfone, polyacylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. 
     
     
       7. The battery of  claim 1  wherein the electrolyte has a hydroxyl content of less than about 1,000 ppm. 
     
     
       8. A lithium salt comprising:
   Li 2 B 12 F x H 12-x-y Z y    
 where x is greater than or equal to 8 and x+y is from 8 to 12, and Z comprises at least one of Cl and Br, and a hydroxyl content of less than about 1,000 ppm and is substantially free of non-lithium cations. 
 
     
     
       9. The salt of  claim 8  wherein the alkali or alkaline earth content, other than lithium, of said salt is less than about 500 ppm. 
     
     
       10. The salt of  claim 8  wherein the total hydroxyl containing impurity level is of said salt is less than about 500 ppm. 
     
     
       11. An electrolyte comprising a combination of at least one lithium salt and at least one organic aprotic solvent, wherein said lithium salt comprises:
   Li 2 B 12 F x H 12-x-y Z y    
 
       where x is greater than or equal to 8 and x+y is from 8 to 12, and Z comprises at least one of Cl and Br, and wherein the electrolyte has a hydroxyl content of less than about 1,000 ppm and is substantially free of non-lithium metal cations. 
     
     
       12. The electrolyte of  claim 11  wherein said at least one solvent comprises at least one member selected from the group consisting of organic carbonates, esters, ketones, and nitriles. 
     
     
       13. The electrolyte of  claim 11  wherein the electrolyte is substantially free of water and HF. 
     
     
       14. The electrolyte of  claim 11  wherein the solvent comprises at least one member selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, bis(trifluoroethyl) carbonate, bis(pentafluoropropyl) carbonate, trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, heptafluoropropyl methyl carbonate, perfluorobutyl methyl carbonate, trifluoroethyl ethyl carbonate, pentafluoroethyl ethyl carbonate, heptafluoropropyl ethyl carbonate, perfluorobutyl ethyl carbonate, etc., fluorinated oligomers, dimethoxyethane, triglyme, dimethylvinylene carbonate, tetraethyleneglycol, dimethyl ether, polyethylene glycols, sulfones, and gamma-butyrolactone. 
     
     
       15. The electrolyte of  claim 11  wherein the electrolyte comprises a gel and comprises at least one solvent selected from the group consisting of polyethers, polyethylene oxides, polyimides, polyphosphazines, polyacrylonitriles, polysiloxanes, polyether grafted polysiloxanes, derivatives of the foregoing, copolymers of the foregoing, crosslinked and network structures of the foregoing. 
     
     
       16. The electrolyte of  claim 11  further comprising at least one member selected from the group consisting of LiPF 6 , lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium tetrafluoroborate, lithium bromide, and lithium hexafluoroantimonate. 
     
     
       17. The electrolyte of  claim 11  wherein x is greater than or equal to 10.